Nanoindentation Studies Research Articles

Rationalizing Distinct Mechanical Properties of Three Polymorphs of a Drug Adduct by Nanoindentation and Energy Frameworks Analysis: Role of Slip Layer Topology and Weak Interactions

Three concomitant polymorphs of 3-((4-chlorophenyl)imino)indolin-2-one, a Schiff’s base, are identified and sorted based on morphology and mechanical response of their crystals. Form I grows as blocks and shows brittle fracture, Form II has long needles and shows plastic bending, and Form III also has long needles and shows elastic bending under similar qualitative mechanical deformation tests. Furthermore, the brittle Form I was found to exhibit thermosalient behavior (jumping) when heated on a hot plate. The distinct mechanical behavior of the three forms is rationalized by analyzing intermolecular interaction energies from energy frameworks analysis, slip layer topology, Hirshfeld surface analysis, and nanoindentation. The quantitative nanoindentation studies unveiled that Form III has higher elastic modulus and stiffness than Forms I and II, while the hardness was lowest for the plastic Form II. Despite high structural similarity in Forms II (plastic) and III (elastic), the E of elastic Form III was f...

High Temperature Flow Behavior of Ultra-Strong Nanoporous Au assessed by Spherical Nanoindentation.

Nanoporous metals have attracted attention in various research fields in the past years since their unique microstructures make them favorable for catalytic, sensory or microelectronic applications. Moreover, the refinement of the ligaments down to the nanoscale leads to an exceptionally high strength. To guarantee a smooth implementation of nanoporous metals into modern devices their thermo-mechanical behavior must be properly understood. Within this study the mechanical flow properties of nanoporous Au were investigated at elevated temperatures up to 300 °C. In contrast to the conventional synthesis by dealloying of AuAg precursors, the present foam was fabricated via severe plastic deformation of an AuFe nanocomposite and subsequent selective etching of iron, resulting in Au ligaments consisting of nanocrystalline grains, while remaining Fe impurities excessively stabilize the microstructure. A recently developed spherical nanoindentation protocol was used to extract the stress-strain curves of nanoporous Au. A tremendous increase of yield strength due to ligament and grain refinement was observed, which is largely maintained at high temperatures. Reviewing literature will evidence that the combined nanocrystalline and nanoporous structure leads to remarkable mechanical properties. Furthermore, comparison to a previous Berkovich nanoindentation study outlines the conformity of different indentation techniques.

Tailoring shear banding behaviors in high entropy bulk metallic glass by minor Sn addition: A nanoindentation study

The present work investigated systematically the glass forming ability, the mechanical properties and the shear deformation of the TiZrHfCuBe high entropy bulk metallic glass (HE-BMG) with minor Sn addition. The results revealed that the glass forming ability and the thermal stability are enhanced by minor Sn addition but within a rather limited composition range. A nanoindentation study of the mechanical response in the (TiZrHfCuBe)1-xSnx (x = 0, 1, 2 and 3 at. %) HE-BMGs showed that the structural heterogeneity caused by Sn addition resulted in higher hardness, larger number of shear bands and smaller size of shear transformation zone, ascribing to the positive enthalpy of mixing between the Sn and Cu/Be elements. A statistical analysis of the serrated flow revealed that the chemical heterogeneities promote a relatively large population of shear deformation units and lead to multiple nucleation of shear bands. The present work might has implications in establishing the link between minor element addition and structure heterogeneity, which is of critical importance for understanding of shear banding behaviors in BMGs.

Nanoindentation study on mechanical properties and curing depth of dental resin nanocomposites

Mechanical properties and curing depth of bisphenol‐α‐glycidyl methacrylate/triethylene glycol dimethacrylate‐based dental composites were systematically investigated by site‐specific nanoindentation tests. Effects of filler (20‐nm silica nanoparticle) content on the nanohardness and elastic modulus of the composites were studied in comparison with micromechanics theoretical models. Results showed that the incorporation of the silica nanoparticles at low contents (up to 5.66 vol%) significantly increases the hardness and elastic modulus of the dental composites by up to 65% and 30%, respectively. It was found that the Counto model gave good predictions for the composite modulus as a function of filler content. For the specific composites studied here, the depth of cure increases approximately linearly with the filler content, which may be ascribed to the stronger reinforcement effect of the silica nanoparticles on the dental composites at a higher particle content. These results combined demonstrate the effectiveness of silica nanoparticles as the reinforcement for dental restorative materials even at small volume fractions. POLYM. COMPOS., 40:1473–1480, 2019. © 2018 Society of Plastics Engineers

Nanoindentation study of mechanical behavior and response of a single layer pristine silicene sheet using molecular dynamics simulations

In the present study, molecular dynamics simulations were carried out to study the mechanical behavior and response of a single layer, rectangular, planar and pristine silicene sheet during nanoindentation process. The nanoindentation simulation on the silicene sheet was done using a spherical diamond indenter and the different force vs depth of indentation curves at different conditions of temperature, indenter radius and depth of indentation were obtained. The variation of mechanical properties like maximum force, hardness and Young’s modulus were studied with respect to temperature, indenter radius and depth of indentation by varying one parameter while keeping the other two parameters constant. The deformation behavior of the silicene sheet up to failure was thoroughly studied and the mechanical properties like maximum force bearing capacity, maximum hardness and Young’s modulus of the silicene sheet were calculated. The maximum force and hardness of the silicene sheet at its maximum indentation depth of 39.5 Å are found to be 286.3 nN and 461.2 GPa respectively. The Young’s modulus of the silicene sheet is found to be 176.9 GPa which is in close agreement with the existing literature reported value of 178 GPa.

Nanoindentation study on the characteristic of shear transformation zone in a Pd-based bulk metallic glass during serrated flow

This paper presents the research on the evolution of shear transformation zone (STZ) in a Pd-based bulk metallic glass (BMG) during serrated flow under nanoindentation. A novel method of estimating the STZ volume through statistical analysis of the serrated flow behavior was proposed for the first time. Based on the proposed method, the STZ volume of the studied BMG at various peak loads have been systematically investigated. The results indicate that the measured STZ volumes are in good agreement with that documented in literature, and the STZ size exhibits an increasing trend during indentation. Moreover, the correlation between the serrated flow dynamics and the STZ activation has also been evaluated. It is found that the STZ activation can promote the formation of self-organized critical (SOC) state during serrated flow.

Nanoindentation study of corrosion-induced grain boundary degradation in a pipeline steel

High-strength low-alloy steels used for oil and gas pipelines are vulnerable to intergranular stress corrosion cracking in moderately alkaline soils. The mechanism of corrosion-induced embrittlement under such conditions is not yet understood. Nanoindentation was used to detect localized degradation of mechanical properties near internal grain boundaries of X-70 steel undergoing intergranular corrosion at active dissolution potentials at pH 8.2. The measurements identified a one-micron thick mechanically-degraded layer with 25% reduced hardness near corroded grain boundaries. It is suggested that the corrosion process may introduce an active softening agent, possibly non-equilibrium lattice vacancies generated by oxidation.

Microstructural and mechanical properties of Al2O3/ZrO2 nanomultilayer thin films prepared by pulsed laser deposition

Single layer aluminium oxide (Al2O3), zirconium oxide (ZrO2) and Al2O3/ZrO2 nano multilayer films were deposited on Si (100) substrates at room temperature by pulsed laser deposition. The development of Al2O3/ZrO2 nanolayered structure is an important method used to stabilize the high temperature phase (tetragonal and cubic) of ZrO2 at room temperature. In the Al2O3/ZrO2 multilayer structure, the Al2O3 layer was kept constant at 5 nm, while the ZrO2 layer thickness varied from 5 to 20 nm (5/5, 5/10, 5/15 and 5/20 nm) with a total of 40 bilayers. The X-ray diffraction studies of single layer Al2O3 indicated the γ-Al2O3 of cubic structure, while the single layer ZrO2 indicated both monoclinic and tetragonal phases. The 5/5 and 5/10 nm multilayer films showed the nanocrystalline nature of ZrO2 with tetragonal phase. The high resolution transmission electron microscopy studies indicated the formation of well-defined Al2O3 and ZrO2 layers and that they are of uniform thickness. The atomic force microscopy studies revealed the uniform and dense distribution of nanocrystallites. The nanoindentation studies indicated the hardness of 20.8 ± 1.10 and 10 ± 0.60 GPa, for single layer Al2O3 and ZrO2, respectively, and the hardness of multilayer films varied with bilayer thickness.

Mechanical properties of 6H-SiC irradiated by neutron and MeV heavy ions: A nanoindentation and finite element method study

Understanding the mechanical properties of structural materials under an irradiation environment stands as a major challenge for developing advanced nuclear systems. In this paper, the mechanical properties, including the Young's modulus, yield stress, and hardness, of SiC samples irradiated by neutron and heavy ions (3 MeV C and Si ions) have been investigated by nanoindentation measurement. When the load-depth curves were analyzed by the widely used Oliver-Pharr method, for the samples irradiated at the same displacement damage level (0.1 and 0.2 dpa), both the elastic modulus and hardness of the ion irradiated SiC are significantly higher compared with those of neutron irradiated samples. The discrepancy is mainly attributed to the irradiation induced surface lateral stress in ion irradiated samples, which cannot be taken into account for the Oliver-Pharr method. After carefully considering this effect by the finite element method in simulating the load-depth curves, both the Young's modulus and yield stress of ion irradiated samples agree well with those of neutron irradiated samples. This study reveals that by the combined method of nanoindentation and finite element, the mechanical properties, including the Young's modulus, yield stress and hardness, for neutron irradiated SiC can be reasonably evaluated by MeV heavy ion irradiation.

Comment on "Incipient plasticity of diamond during nanoindentation" by C. Xu, C. Liu and H. Wang, RSC Advances, 2017, 7, 36093.

A recent molecular dynamics simulation study on nanoindentation of diamond carried out by Xu et al.1 has reported observation of the presence of a controversial hexagonal lonsdaleite phase of carbon in the indentation area. In this comment, we question the reported observation and attribute this anomaly to shortcomings of the long range bond order potential (LCBOP) employed in the nanoindentation study.

Deposition and Characterization of Aluminium Thin film Coatings using DC Magnetron Sputtering Process

Aluminium (Al) thin film deposited using DC Magnetron sputtering combines many properties such as Optical, Mechanical properties on ceramic substrates .Properties of thin film coating depend on the deposition parameters employed. The aim of this work was to study the optical and mechanical properties of aluminium thinfilms. In order to study the above property deposition parameters varied with different deposition rate, power and argon flow rate in the DC magnetron sputtering process on substrates. The films were characterized by atomic force microscope, UV VIS NIR spectrophotometer, thickness profiler and nano mechanical testing system. The surface morphology of the film was examined by atomic force microscope shows the dense and uniform nanostructures with increased surface roughness from 4 to 21 nm with increasing argon flow. UV-VIS-NIR Spectrophotometer analysis indicates higher reflectance for all the films in the wavelength range of 250 nm to 2500 nm. Nano indentation study revealed that there was a considerable change in hardness values of the films prepared at different conditions.

Synthesis and characterisation of nanocrystalline, microcrystalline and functionally graded diamond coatings on reaction bonded SiC

Nanocrystalline diamond (NCD) films on different substrates have the potential for use in various tribological, thermal management and other applications. On the other hand, microcrystalline diamond (MCD) coatings exhibit higher hardness and better adhesion on many substrates. Hence, the realisation of a functionally graded MCD-NCD coating on a substrate have a high applicability, particularly for tribological and wear-related applications. In this study, reaction bonded silicon carbide was used as a substrate for the deposition and growth of NCD, MCD and functionally-graded NCD-MCD films using a large area hot filament chemical vapour deposition (HFCVD) equipment. The microstructure of the film was controlled by suitably adjusting the methane to hydrogen flow rate ratios during deposition. Characterization by high resolution scanning electron microscopy (HRSEM), atomic force microscopy (AFM), x-ray diffraction (XRD) and Raman spectroscopy confirmed the nature and microstructure of the coatings. Nanoindentation studies revealed the hardness values to lie in the range of 25 GPa for the NCD coating to 38 GPa for the MCD film, which drastically increased to 70 GPa when the thickness of the coating was reduced by changing the deposition time. The results of these studies on the NCD, MCD and functionally-graded NCD-MCD coatings are compared and contrasted.

AFM and nanoindentation study of selected aluminium alloys

AFM and nanoindentation study of selected aluminium alloys

Surface modification of Al6061 by graphene impregnation through a powder metallurgy assisted friction surfacing

Impregnation and homogeneous distribution of nanomaterials on metallic surfaces have always been a challenge for researchers in recent times. In the present work, authors demonstrate a surface modification of Aluminium by graphene impregnation through a novel powder metallurgy assisted friction surfacing (PMAFS) process. This modified friction surfacing technique involves two stages. In the first stage, an Aluminium-graphene composite tool is fabricated through a powder metallurgy route. In the second stage, this consumable tool is utilized for FS to obtain a composite coating layer on Aluminium surface. Experimental results show that the surface composite prepared by this modified friction surfacing technique does have impregnated graphene successfully in Al matrix. The obtained surface composites were characterized by using SEM, TEM, and XRD. Morphology and damage to graphene are studied by using Raman spectroscopy. Nanoindentation study was conducted for a various set of processing parameters with variation in graphene content. Further, the influence of graphene percentage and processing parameters on mechanical properties and microstructural changes were also studied. Composites prepared at relatively lower tool rotational speed with low content of graphene in the tool is found to have optimum mechanical properties with a homogeneous distribution of graphene in Al substrate. The nano-hardness of the surface composite is increased by 100% after impregnation of graphene nano platelets (GNP) with an optimum set of parameters.

Microscopic plastic response in a bulk nano-structured TiAl intermetallic compound processed by high-pressure torsion

Intermetallic compounds of titanium aluminides (Ti-Al) have attracted much attention for their excellent properties including light-weight, high specific strength and high-temperature creep strength. Nevertheless, bulk Ti-Al require suitable processing routes for improving the mechanical properties, especially plasticity and ductility. Accordingly, the present study applies a strategy of grain refinement through high-pressure torsion (HPT) processing which is an effective processing technique for difficult-to-work alloys due to the large compressive hydrostatic stresses that are developed during processing. A γ-based Ti-45Al-7.5Nb intermetallic compound was processed by HPT for 5 and 10 turns under 6.0GPa at room temperature. The duplex microstructure was successfully refined to have ultrafine laths with thicknesses of 40–100nm after 10 HPT turns. Improved hardness was recorded by both Vickers microhardness and nanoindentation measurements. The X-ray diffraction profiles confirmed the occurrence of phase transformation from γ-TiAl to α2-Ti3Al after HPT. The macroscopic plastic flow was estimated through the nanoindentation technique by applying both Berkovich and spherical indenters. The results predict an improved plastic behavior by increasing the strain rate sensitivity and a significant increase in yield strength whereas a slight decrease is measured in the strain hardening capability after HPT for 10 turns. Furthermore, this nanoindentation study demonstrates an alternative and promising technique of small-scale testing for predicting the macroscopic plastic flow behavior of ultrafine-grained materials.

Theoretical and experimental study of the stiffness of electrospun composites of poly(vinyl alcohol), cellulose nanofibers, and nanohydroxy apatite

The present study aims to theoretically model and verify the mechanical behavior of electrospun fibers of poly(vinyl alcohol) (PVA) reinforced by nanohydroxy apatite (nHAp) and cellulose nanofibers (CNF), the three composites designated as PVA/nHAp, PVA/CNF, and PVA/nHAp/CNF. Tensile tests and AFM nanoindentation studies were used to measure tensile modulus of electrospun scaffolds and single fibers respectively. Halpin–Tsai and Ouali models were applied to predict the stiffness of electrospun mats. Theoretical analysis according to the Halpin–Tsai model showed that CNF have no preferred orientation in the electrospun fibers, particularly at higher filler content. Additionally, this model provided a better prediction than Ouali model, especially at lower filler content. Theoretical models based on the geometry of an unit cell in open-cell structure such as honeycomb, tetrakaidecahedron and cube models simulate electrospun scaffolds. Among the structural models for analysis of porous scaffolds, the honeycomb model showed the best prediction, tetrakaidecahedron model—a moderate one, and cube model was the worst. In general, it was proved by both experiment and theory that the porous structure of electrospun mat caused significant modulus reduction of nanocomposites.

Influence of carbon nanotubes structures embedded in UHMWPE on bacterial adherence

ABSTRACTBecause of their intrinsic properties, carbon nanotubes (CNTs) have been suggested for biomedical applications. We studied the anti-adherent performance of two ultra-high-molecular-weight polyethylene (UHMWPE) surfaces which contains 3% multi-wall CNT variant (MWCNT): Nanocyl/UHMWPE and Arc/UHMWPE. These surfaces were obtained by hot pressure forming after mechanical mixture. Additional nanoindentation studies were performed and hardness and stiffness were determined. Mechanical properties of the MWCNT/UHMWPE composites were also compared to raw UHMWPE and correlated with their anti-adherent performance. Comparing with UHMWPE, Nanocyl/UHMWPE was the least adherent surface. Bacterial adherence was also significantly reduced in Arc/UHMWPE for four strains.

Indentation in single-crystal 6H silicon carbide: Experimental investigations and finite element analysis

Silicon carbide (SiC) is a promising material ideally suited for small-scaled devices deployed in harsh environments. SiC is brittle in bulk form, however, at small component length-scales plasticity is observed. A good understanding of deformation behaviour is, therefore, crucial for reliable small-scale component design and fabrication. Here, experimental and numerical analysis of the deformation behaviour of single-crystal 6H-SiC in nanoindentation is presented. Nanoindentation studies are carried out in two orientations of the single-crystal using a Berkovich indenter. Next, a crystal-plasticity theory was implemented in finite-element (FE) modelling framework to predict the deformation of the hexagonal single-crystal. The validity of the present FE modelling methodology was corroborated through comparison between FE simulations and experimental data in terms of indent profile and load-displacement curves. Our results showed that classical crystal plasticity theory can be reliably applied in predicting plastic deformation of ceramic at small scales.

Nanoindentation study of the creep behavior in a Fe-based bulk metallic glass

In this paper, the creep behavior of a Fe-based bulk metallic glass (BMG) was studied by using the nanoindentation testing. According to the microstructural evolution in BMGs, the generalized Kelvin model was employed to describe the creep behavior of this BMG, and a method of separating the viscoelastic and viscoplastic deformation from the indentation creep was proposed. The creep behaviors at various loading rates were systematically analyzed. The obtained results indicated that the viscoelastic or viscoplastic characteristics of Fe-based BMG exhibited a strong dependency on the loading rate. Moreover, the volume of shear transformation zone (STZ) during the creep of Fe-based BMG has also been calculated to further explore its creep mechanism.

Nanoindentation study of the interfacial zone between cellulose fiber and cement matrix in extruded composites

The present study shows the application of the nanoindentation technique to evaluate the properties of the cellulose fiber-cement matrix interfacial zone in composites prepared with an auger extruder. The degree of strength of the bond between fiber and matrix is recognized as important variable that influences macro-mechanical properties, such as modulus of rupture and toughness of cement based composites. The nanoindentation measurements showed the highest hardness and elastic modulus in the part inner of the cellulosic fiber after hydration process due to precipitation and re-precipitation of cement hydration products. These results indicate that mineralization of the cellulosic fibers can affect the stress distribution and interfacial bond strength in the cement based composite.